Please provide more information. What is your system and Firefox? What happens when Firefox is called?

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox. Is the problem still there?

Hi Peg, could you describe where the process is breaking down?

For example, when you double-click the Firefox desktop icon, do you get a message such as Firefox is already running, or your profile can't be found, etc.

Or does the Firefox window never appear at all?

If the window appears, do you get a blank page, or server not found, or some other specific message?

And which site are you trying to go to?